Author: Gareth Crouch
Crouch, Gareth, 2016 Early and late effects of transcatheter aortic valve implantation on myocardial function, myocardial injury and valve haemodynamics, Flinders University, School of Medicine
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Objectives
There remains a paucity of mechanistic data on the effect of transcatheter aortic valve implantation (TAVI) on left and right ventricular function and the clinical impact of these effects. We sought to assess and compare the effects on myocardial function and aortic valve haemodynamics of transcatheter (TAVI) and aortic valve replacement (AVR) utilizing serial cardiovascular magnetic resonance (CMR) and echocardiography. The time points selected were pre-procedure, early post-procedure (<14 days) and late post procedure (12 months). The impact of these changes on clinical endpoints will also be examined. Finally we compared CMR and transthoracic echocardiography (TTE) analysis of pre-operative and post-operative aortic regurgitation in patients undergoing both TAVI and AVR. Paravalvular aortic regurgitation (PAR) following TAVI is well recognised as a complication with a deleterious effect on outcome. Despite improvements, echocardiographic measurement of PAR largely remains qualitative whereas CMR directly quantifies AR with accuracy and reproducibility.
Methods
To assess early outcomes a prospective comparison study of 47 patients with severe aortic stenosis undergoing either TAVI (26) or high risk AVR (21) was conducted. CMR (for LV/RV function, LV mass, left atrial volume and aortic regurgitation) was carried out pre-procedure and early post-procedure (<14 days). To compare the assessment of PAR, eighty-seven patients with severe aortic stenosis undergoing TAVI (56 patients) or AVR (31) were assessed. CMR (1.5T) and transthoracic echocardiography (TTE) were carried out pre-operatively and a median of 6 days post-operatively. The CMR protocol included regurgitant aortic flows using through-plane phase-contrast velocity. At late follow-up 32 patients (19 TAVI, 13 AVR) underwent CMR (for LV/RV function, LV mass, AV haemodynamics). Finally late clinical follow-up using a combined endpoint was conducted on 38 patients.
Results
Groups were similar with respect to STS Score across all analyses, however TAVI patients were older. Preoperative left ventricular and right ventricular ejection fractions were similar. In the study of early outcomes post-operative LVEF was preserved in both groups. In contrast, decline in RVEF was more significant in the TAVI group (61% to 54% vs. 59% to 58%, p=0.01). Post-procedure aortic regurgitant fraction was significantly greater in the TAVI group (16% vs 4%, p=0.001), as was left atrial size (110mls vs. 84mls, p=0.02). Further analysis revealed a significant relationship between the increased aortic regurgitant fraction and greater left atrial size (p=0.006), and a trend towards association between the decline in RV dysfunction and increased post-procedure AR (p=0.08). The analysis of post-procedure aortic regurgitant fraction using CMR demonstrated greater regurgitation in the TAVI group (TAVI 16±13% vs. AVR 4±4%, p<0.01). Comparing CMR to TTE, 27 of 56 (48%) TAVI patients had PAR which was at least one grade more severe on CMR than TTE (Z = -4.56, p <0.001). Sensitivity analysis confirmed the difference in PAR grade between TTE and CMR in the TAVI group (Z = -4.49, p < 0.001). Finally the study of late outcomes showed no difference in late LVEF or RVEF between TAVI and AVR. Late regurgitant fraction remained elevated in the TAVI group. In the 38 patients with late clinical follow-up there was an association between the combined endpoint (death, MI, CVA, PPM, Readmission) and impaired LV function and RV function, pre and post-procedure.
Conclusion
There was no significant difference in early left ventricular systolic function between techniques. While RV systolic function was preserved in the AVR group, it was significantly impaired early after TAVI, possibly reflecting a clinically important pathophysiologic consequence of paravalvular aortic regurgitation. Regarding paravalvular aortic regurgitation, TTE underestimated the degree of paravalvular aortic regurgitation when compared to CMR based quantitative analysis. This underestimation may in part explain the findings of increased mortality associated with mild or greater AR by TTE in the PARTNER trial. Paravalvular aortic regurgitation post TAVI assessed as mild by TTE may in fact be more severe. Finally there was no significant difference in either left or right ventricular function at 12 months. There was however an association between both pre- and early post-procedure left and right ventricular function and a worse late outcome.
Keywords: TAVI, AVR, CMR, cardiac magnetic resonance, transcatheter valve, right ventricular function, myocardial injury
Subject: Medicine thesis, Surgery thesis
Thesis type: Masters
Completed: 2016
School: School of Medicine
Supervisor: Prof Joseph Selvanayagam